The basic research objective is to improve radiation therapy in human cancer, especially to eliminate the danger of increased metastasis following certain instances of such therapy. The possibility to increased metastasis is suggested by X-irradiation experiments in animals extending from 1957 to the present time. These experiments showed that a focally irradiated area in rabbits and in rats loses much of the natural characteristic to localize injected foreign substances. Tissue localization of injected foreign substances in normal animals is especially marked in the skin. But irradiation of a given area of the skin breaks down the localizing capacity in that area. Thus, virulent bacteria, diphtheria toxin or foreign protein injected in an irradiated area of rabbits rapidly reach the blood stream. The rapidity of escape from the injected area is shown by the fact that the bacteria or diphtheria toxin may escape from the area before a local lesion is produced and lead to death. Walker 256 tumor cells injected in an irradiated area of Sprague-Dawley rats showed metastasis in the liver and kidneys, while the nonirradiated controls show less metastasis. It is planned first, to investigate the relationship between irradiation and metastasis, particularly to determine which method of irradiation in cancer favors metastasis and which method reduces metastasis. Second, to investigate immunologic aspects of localization with special reference to biochemical factors. This plan would also embrace the mechanism of tissue localization in immunity in the absence of irradiation. Third, it is proposed also to combine irradiation of cancer in animals with anti-cancer and anti-inflammatory drugs as a means to effect metastasis. Fourth, preliminary experiments indicate also that Interferon or Interferon inducers may either increase localization or reduce metastasis without regard to localization in certain tumors.